li:first-of-type {
  background-color: red;
}
li:last-of-type {
  background-color: pink;
}
li:nth-child(even) {
  background-color: aqua;
}
li:nth-child(odd) {
  background-color: rgb(27, 29, 29);
}
/* 表单 */
.input1:disabled {
  background-color: #fff;
}

@media screen and (min-width: 300px) {
  body {
    background-color: lightblue;
  }
}
